1. Field of the Invention
The present invention relates to an alkaline fuel cell containing a hydrogen-releasing agent. More particularly, the present invention relates to a fuel cell or secondary cell which comprises an oxygen electrode as a cathode and a hydrogen storage alloy electrode as an anode in an aqueous alkaline solution of electrolyte containing a novel hydrogen-releasing agent.
2. Description of the Prior Art
Fuel cells produce current directly by the electrochemical reaction of hydrogen with atmospheric oxygen. Such cells are classified into alkaline fuel cells(AFC) and phosphoric acid fuel cells(PAFC) depending on the type of the electrolyte employed.
Generally, fuel cells of the type whose anode is directly supplied with hydrogen gas have been hitherto utilized because the electrochemical reaction has a high efficiency and can also occur at a normal temperature when hydrogen fuel is supplied as a gas. However, the hydrogen fuels have the disadvantages that their storage density is lower than that of other fuels, and thus their economical efficiency is low.
In the meantime, studies of producing fuel cells of the type which employ a hydrogen-containing hydrocarbon compound such as methane, propane, methanol, hydrazine, ammonia, and the like in place of the hydrogen gas in the solution of electrolyte, or of the type which supplies such a compound for the anode, have been developed. However, such fuel cells have the disadvantage that they require high temperatures (e.g., above 300.degree. C.) for effective oxidation/reduction reactions of hydrogen/oxygen and that the reaction rate is slower. Thus, the reaction efficiency is degraded as compared with cells using hydrogen gas.
We, the inventors, have extensively studied approaches for overcoming these prior art disadvantages. As a result, we have discovered that where a hydrogen-releasing agent selected from the group consisting of NaBH.sub.4, KBH.sub.4, LiAlH.sub.4, KH and NaH is added to an aqueous alkaline solution of electrolyte as hydrogen fuel, the electrochemical reaction rate is higher at a normal temperature compared with cells containing other hydrogen fuels.